The invention relates to fire alarms or detectors, and to their installation.
As known for the protection of human life and material assets, fire alarms may be included in early-warning fire-alarm systems. Such a system typically includes a signaling and control center, and fire alarms distributed in the premises to be protected.
The fire alarms include fire sensors, electronic amplifiers, and means for communicating information to the signaling and control center. Typically, a fire alarm assembly consists of the fire alarm proper, called alarm insert, including one or several sensors with electronic circuitry, and of an alarm base or mounting which is permanently installed in the premises to be protected and into which the alarm insert is inserted. Thus, the alarm inserts can be removed for service and then reinserted.
Since fire alarm systems have to meet stringent reliability standards, weak spots must be eliminated to the extent possible. Undoubtedly in this regard, a reliable connection between the fire alarm insert and its base is required for dependable functioning of the fire alarm system. Reliability of connection depends on alarm design and is an important consideration in alarm development.
The following are among requirements to be met by the connection between the alarm base and the alarm insert: reliable electrical contact, protection of the contacts against contamination and corrosion, reliable mechanical attachment, and pleasing appearance. The latter requirement arises especially in surroundings where aesthetics play a role, e.g., in theaters, museums and historical buildings.
As a design which combines pleasing appearance with protection against contamination of contacts, German Patent Document DE-U1-9210858 discloses an alarm insert which completely covers the base upon insertion. Advantageously further in this design, discoloration of the base due to aging does not detract from the appearance of the alarm, e.g., upon later replacement of the alarm insert.
Alarms in accordance with German Patent Document DE-U1-9210858 suffer from a drawback in that, with the alarm base completely covered by the alarm insert, it is difficult to determine whether the insert has been properly inserted in the base. Proper insertion of the alarm in the base is a key condition for proper functioning, and improperly inserted alarms are sources of errors and of malfunctioning giving rise to complaints.
In the past, this shortcoming did not receive proper attention, until it was realized that proper positioning of alarms had to be verified by trained technicians. The attendant additional effort and costs of installation are unavoidable in the interest of functional integrity of the system.